This invention relates to a safety device which may be used by climbers, construction workers or other persons working at height to arrest the person in case of a fall. The device is of the type in which a line or cord is payed out from a spool.
Generally, the protection offered by spool and cord type safety devices resides in that a person attached to the device cannot fall further than the length of the cord. Thus, if the cord is short enough, the gravitational acceleration over the distance available for the drop cannot result in a higher drop speed than such as would, even in case of sudden breaking and direct impact, cause at most painful bruising but certainly not serious bodily harm to the person falling. Therefore, in order to insure its safe functioning, the length of the cord should not exceed a certain limit.
The considerable restriction of movement of the secured person is eased in a safety device according to DAS 1,299,402 by the fact that the center of rotation of pawls on the spool inside the casing to which the cord is attached and around which it is coiled, are located in such a way that the centrifugal force created by the rotation of the spool extends the pawls and presses them against the teeth of a gear rim forming part of a friction brake.
Such a device allows the extension of the cord over any part of its length, as long as the cord extraction speed does not exceed a critical point at which the friction brake is activated and a slight braking occurs. However, the device is a rather complex construction and is rather heavy.